1. Field of the Invention
The present invention relates to a tubular insertion device which comprises a tubular insertion portion including a flexible portion in a predetermined part.
2. Description of the Related Art
One known tubular insertion device in which a flexible cylindrical tube is inserted into a lumen is configured to detect the shape of the cylindrical tube by using an optical fiber for shape detection. For example, according to the disclosure in Jpn. Pat. Appln. KOKAI Publication No. 2001-169998, optical fibers for shape detection are arranged on the outer circumferential surface of a cylindrical tube so that bending detectors are located with predetermined intervals. These optical fibers are joined together in the longitudinal direction of the cylindrical tube to combine bending amounts of bending detection points so that the shape of the whole cylindrical tube can be detected.
Another known tubular insertion device in which a cylindrical tube is inserted into a lumen is configured so that a force sensor is disposed in the flexible cylindrical tube to detect an external force applied to the cylindrical tube. For example, according to a configuration shown in Jpn. Pat. Appln. KOKAI Publication No. 6-154153, strain gauges are arranged on the outer circumferential surface of a cylindrical tube to detect an external force applied to the outer circumferential surface of the cylindrical tube.
When the cylindrical tube is inserted into the lumen, the cylindrical tube is inserted while sometimes contacting the inner wall of the lumen. Therefore, when the lumen is rigid and twisting, there is a possibility that the distal end of the cylindrical tube may be worn and broken if the cylindrical tube is inserted by excessive force. When such lumen is soft, there is a possibility that the lumen may be damaged if the cylindrical tube is inserted by excessive force. To avoid this, it is preferable to know the external force applied to the cylindrical tube as operation support information when inserting the cylindrical tube.
According to Jpn. Pat. Appln. KOKAI Publication No. 2001-169998, although it is possible for an operator to know the shape of the tube as the operation support information regarding the cylindrical tube, it is not possible for the operator to know, for example, information regarding the external force applied to the tube. In the meantime, according to Jpn. Pat. Appln. KOKAI Publication No. 6-154153, it is possible to detect an external force applied to the tube from a particular direction. However, if the external forces applied to the tube from various directions are taken into consideration, it is necessary to attach a considerably large number of strain gauges. This leads to the following problems: the outer shape of the cylindrical tube is increased in size; the flexibility is hindered when a large number of wiring lines and sensors are attached; or a significant number of wiring lines for sensors are required.